Form of sugar (7)
I believe the answer is:
glucose
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">form of sugar</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for glucose that I've seen before include "Blood sugar" , "Sweet substance" , "Naturally occurring sugar" , "Simple sugar" , "Type of sugar" .)